1. Field of the Invention
The invention relates to a switched capacitor circuit, and more particularly to a switched capacitor circuit with switching loss compensation mechanism.
2. Description of the Related Art
FIG. 1 shows a conventional single-ended parallel resonant circuit with loss. When the parallel resonant circuit is used as a differential circuit, the capacitor C can be realized using the switched capacitor circuit 900 as shown by FIG. 2. The conventional switched capacitor circuit 900 includes a plurality of N type transistors 901˜903 and a plurality of capacitors 904˜905. The switched capacitor circuit 900 is used to perform a capacitor switching action between a positive voltage terminal NVp and a negative voltage terminal NVm of a differential circuit, thereby switching equivalent capacitances of NVp and NVm relative to ground. The N type transistors 901˜903 are responsive to a switching signal Sc. The parallel resonant circuit has the characteristics according to the following formula:
      R    T    =                              (          Q          )                2            ·              R        s              =                                        (                                          ω                ⁢                                                                  ⁢                L                                            R                s                                      )                    2                ·                  R          s                    =                                    (                          1                              ω                ⁢                                                                  ⁢                                  CR                  s                                                      )                    2                ·                  R          s                    
Further referring to FIG. 3, which is a frequency response of a resonant circuit in the switched capacitor circuit 900, when Sc takes the value 0, each of NVp and NVm is still connected to a capacitor (not shown). As can be seen from FIG. 3 and the above formula, when the capacitance value of the switched capacitor circuit 900 is increased, and when the switching signal Sc switches from 0 to 1, the mid-point resonant frequency of the resonant circuit decreases from fc1 to fc2, and the amplitude of the mid-point frequency decreases from Amp1 to Amp2, resulting in the difference in the amplitude on the same usable bandwidth, and further resulting in the unevenness inside the bandwidth and decrease in the operating effectiveness of the resonance of the resonant circuit.